Makefile: Optimize with -Og for DEBUG=1
Makefile: Optimize with -Og for DEBUG=1

vboot has grown code that requires optimizations (notably dead code
elimination) to be enabled to work right and avoid linker reference
errors. For example, the VB2_TRY() macro may or may not emit a call to
vb2api_fail(), based on whether a `ctx` argument was passed. This is
done through an if-statement with a compile-time constant condition, but
the compiler will only actually omit the vb2api_fail() call instruction
when optimizations are enabled. Not all vboot build targets (e.g.
hostlib) provide the vb2api_fail() symbol, so disabling optimizations
may cause link failures for those targets.

GCC and clang offer an -Og option that only enables simple optimizations
(like dead-code elimination) which don't interfere with debugging...
let's just use that instead.

BRANCH=None
BUG=None
TEST=None

Signed-off-by: Julius Werner <4d12f06cff3725783b352157673a720bc67c4afe@chromium.org>
Change-Id: Ia972dc498839df80af6ccae8a8203e8c63a5eadc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2986801
Reviewed-by: Joel Kitching <c2feea8c1334a0d339e816ae4c7c9ecfa9b30a91@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot